Well, my YT channel is not monetized, so I can not make a direct comparison in regard to income. I did notice that on YT I often get more views from Facebook than from YT, so posting the links elswhere can't hurt. I think the biggest benefit from Steemit comes from having a way to get into Crypto currency without shelling out cash. Also since Steemit is a new platform you won't face competition from the long established channels that seem to enjoy favor in YT and on Steemit/DTube you get rewarded right away without being "advertiser friendly". In other words, the viewer decides what's worth watching instead of the same corporations that are killing Print, Radio and TV by withholding advertising dollars. That being said; YT is fantastic in it's features and sound/image quality. If those are qualities that matter to you, you could use both, YT for the video and Steemit for articles providing further information. I hope this gives a bit of insight into the difference between the 2. In your shoes I would probably concentrate on the platform where the numbers grow the fastest and that may well be DTube/Steemit.